The present invention relates generally to automotive ignition coil assemblies and, in particular, to an ignition coil retaining clip for use in an automotive engine compartment.
Ignition coil assemblies for automotive spark-ignition internal combustion engines are well known. Spark-ignition internal combustion engines require the use of spark plugs to ignite a fuel-air mixture that has been introduced into the various combustion cylinders of the engine. The spark plugs are typically disposed in threaded holes in the cylinder head. One end of each spark plug includes gapped electrodes and extends into the combustion cylinder. An opposite end of each spark plug includes an electrical terminal and extends outwardly from the cylinder head.
In order to generate a spark across the gapped electrodes, each spark plug requires a supply of electricity that is provided by an ignition system. Traditionally a single ignition coil was used connected to the spark plugs by a distributor. More recently, an ignition coil assembly, provided for each spark plug, is a component of the ignition system and includes both a wound primary coil and a wound secondary coil. The secondary coil of each coil assembly is electrically connected to the terminal of each spark plug. At the proper time in the engine operating cycle for firing a particular spark plug, electric current flowing through the primary of the respective ignition coil assembly is abruptly interrupted to induce a voltage in the secondary coil sufficiently high to create a spark across the gapped electrodes of the spark plug, igniting the combustible fuel-air mixture to power the engine.
Prior art ignition systems utilize various types of ignition coil assemblies. One type of ignition coil assembly is inserted substantially inside the spark plug insertion bore in the cylinder head combustion engine. This type of coil assembly is known in the art by various names including a pencil coil, a stick coil, a plug hole coil, and a cigar coil. Another type of ignition coil assembly includes a boot that is retained in the engine cover. The magnetic circuit components, including the primary and secondary coils, of this type of ignition coil are housed above the spark plug insertion hole and attached to the boot. This type of coil assembly is known in the art by various names including a coil on plug, plug top coil, and coil per plug.
Regardless of the type of ignition coil assembly, prior art ignition coil assemblies typically have been mounted to a mounting surface in the engine compartment, such as the cam cover or the cylinder head, by an external bracket or mounting arm. A fastener extends through the bracket or mounting arm to fasten the assembly the mounting surface. Many prior art ignition coil assemblies brackets or mounting arms, however, are formed as an integral part of the assembly, disadvantageously limiting the use of the assembly to a single application. If any changes are made to the mounting surface, or if the assembly is desired to be used in a different application, extensive and expensive tooling modification to the assembly is required. Once manufactured, these prior art ignition coil assemblies also require the use of fasteners and occasionally special tools when the assemblies are attached to the mounting surface.
It is desirable to improve on these prior art means for attaching ignition coil assemblies by providing a means for attaching the ignition coil to the engine that is not limited to a single application. It is also desirable to provide a means for attaching the ignition coil to the engine without requiring the use of fasteners or special tools.
It is an object of the invention, therefore, to provide a simple and quick method of attaching ignition coils to a mounting surface within the engine compartment that does not require the use of fasteners or special tools.
The present invention concerns a retaining clip for attaching a component, preferably an ignition coil assembly, to a mounting surface, such as the cam cover, the cylinder head, or the spark plug, in an internal combustion engine compartment.
The generally U-shaped retaining clip includes a base member having two side members or legs extending transversely from opposite ends. Locking tabs extend outwardly from a lower portion of the exterior surface of each of the side members. The interior surfaces of each of the side members and the base member are shaped to conform to an upper boot portion of the ignition coil assembly.
The boot portion of the ignition coil assembly typically contains the magnetic circuit components and is adapted to receive the retaining clip. An intermediate umbrella portion is attached below the boot portion and includes a sealing surface attached thereto. A lower portion for attaching to the spark plug extends downwardly from the umbrella portion. The ignition coil assembly is typically constructed of metal and overmolded with an elastomeric material, such as liquid silicon rubber material. Apertures in the sealing surface of the umbrella portion receive the lower portion of the side members when the retaining clip is attached to the ignition coil assembly, forming an ignition module. The overmolded silicon rubber material of the sealing surface deflects to receive the lower portion of the side members, forming an interference fit between the walls of the apertures in the sealing surface and the exterior surface of the side members. The lower portion of the side members extends downwardly beyond the sealing surface of the ignition coil.
Apertures in the mounting surface receive the lower portions of the side members that extend downwardly beyond the sealing surface of the ignition coil. The mounting surface is adapted to receive the ignition module and the locking tabs of the side members cooperate with corresponding locking grooves on the mounting surface to hold the module in place on the mounting surface.
During assembly, the installer simply inserts the boot end of the module into the spark plug insertion hole on the engine. The side members on the module coincide with grooves on the mounting surface, advantageously allowing only one possible assembly scenario. Once the module is calibrated to the proper orientation, the installer simply pushes the module into the aperture in the mounting surface. The locking tabs on the module flex inwardly during insertion and then spring back when forced past a specific depth in the apertures and the locking tabs of the side members engage with the locking grooves on the mounting surface.
Once the module is seated, the locking tabs retain the module to the mounting surface, allowing the umbrella portion to apply a constant force against the locking tabs to help keep the module tight on the mounting surface. The high voltage connection with the spark plug can be accomplished by traditional means of a compression spring contact that is fixed to the module. The ignition coil module is preferably removed by squeezing the side members at the top of the module. Alternatively, the ignition coil module is removed by separating the side members at the top of the module. The retaining clip can be made of a variety of different materials including, but not limited to, plastic.
The retaining clip may be attached to the module in a variety of different ways including, but not limited to, an interference fit with the umbrella portion of the ignition coil assembly or overmolding the retaining clip with the same liquid silicon rubber that encapsulates the module. Alternatively, the retaining clip can be molded as part of another piece of the module such as a housing or bobbin.
The present invention advantageously eliminates the need for an external mounting arm configuration of the prior art that requires a bolt type fastener. As a result, there are no extra fasteners or tools needed to install or remove the module, thereby requiring fewer parts to attach the ignition coil assembly to the engine, and reducing the cost of the ignition coil assembly.
The present invention is especially suited for attaching xe2x80x9ccoil-on-plugxe2x80x9d and xe2x80x9cpencilxe2x80x9d type ignition coils to a mounting surface but may also be adapted for use with other types of ignition coils. Because the present invention eliminates the use of fasteners, the present invention also eliminates the need for a boss or projection extending from prior art mounting surfaces to receive the fastener. As a result, the present invention permits xe2x80x9cpencilxe2x80x9d type ignition coil assemblies to be virtually hidden in the engine spark plug hole, allowing for a visually appealing low profile design after assembly.
The present invention advantageously reduces the assembly time and the number of parts required to attach the ignition coil assembly to the mounting surface and simplifies the manufacturing, assembly, and attachment processes.
The actual dimensions of the base members and side members may be varied to fit the various profiles of the component that is to be attached to the mounting surface, all while remaining within the scope of the present invention.